The reunited Empire would not last. During a coup led by his nephew Arnulf of Carinthia in November 887, Charles was deposed in East Francia, Lotharingia, and Italy. Forced into quiet retirement, he died of natural causes in January 888, just a few weeks after his deposition. The Empire quickly fell apart after his death, never to be restored, with the Empire splintering into five separate successor kingdoms.

Usually considered lethargic and inept – he is known to have had repeated illnesses and is believed to have suffered from epilepsy – he twice purchased peace with Viking raiders, including at the famous siege of Paris in 886. Nevertheless, contemporary opinion of him was not nearly so negative as modern historiographical opinion.

Charles was the youngest of the three sons of Louis the German, first King of East Francia, and Emma, a Welf. An incident of demonic possession is recorded in his youth, in which he was said to have been foaming at the mouth before he was taken to the altar of the church. This greatly affected his father and himself. He was described as "a very Christian prince, fearing God, with all his heart keeping His commandments, very devoutly obeying the orders of the Church, generous in alms-giving, practising unceasingly prayer and song, always intent upon celebrating the praises of God."[citation needed]

In AD 859, Charles was made Count of the Breisgau, an Alemannic march against southern Lotharingia.[2] In 863, his rebellious eldest brother Carloman revolted against their father. The next year, Louis the Younger followed Carloman in revolt and Charles joined him. Carloman was invested with Bavaria as co-king. In 865, the elder Louis was forced to divide his lands among his heirs: Bavaria went to Carloman; Saxony (with Franconia and Thuringia) went to Louis; and Alemannia (Swabia with Rhaetia) went to Charles. Lotharingia was to be divided between the younger two.

When, in 875, the Emperor Louis II, who was also King of Italy, died, having come to terms with Louis the German whereby Carloman would succeed in Italy, Charles the Bald of West Francia invaded the peninsula and had himself crowned king and emperor.[3] Louis the German sent first Charles and then Carloman himself, with armies containing Italian forces under Berengar of Friuli, their cousin, to possess the Italian kingdom.[3][4] This was not, however, successful until the death of Charles the Bald in 877.

In 876, Louis died and the inheritance went as planned after a conference at Ries, though Charles received less of his share of Lotharingia than planned. In his charters, Charles' reign in Germania is dated from his inheritance in 876.

The brothers acted cooperatively and avoided any war over the division of the patrimony: a rare occurrence in Dark Age Europe. In 877, Carloman inherited Italy from their uncle Charles the Bald of West Francia. Louis divided Lotharingia and offered a third to Carloman and a third to Charles. In 878, Carloman returned his Lotharingian share to Louis, who then divided it evenly with Charles. In 879, Carloman was incapacitated by a stroke and divided his domains between his brothers: Bavaria to Louis and Italy to Charles. Charles dated his reign in Italia from this point, and from then he spent most of his reign until 886 in his Italian kingdom.[5]

In 880, Charles joined Louis III and Carloman, joint kings of West Francia, in besieging Boso of Provence in Vienne from August to September but they failed to dislodge him. Provence was legally a part of the Italian kingdom (from 863). In August 882, Charles sent Richard the Justiciar, Count of Autun, to take the city, which he did (in September). After this, Boso could not regain most of his realm and was restricted to the vicinity of Vienne.

On 18 July 880, Pope John VIII sent a letter to Guy II of Spoleto to seek peace, but the duke ignored him and invaded the Papal States. John responded by begging the aid of Charles in his capacity as King of Italy. In gratefulness, he crowned him Emperor on 12 February 881. His rise to power was accompanied by hopes of a general revival in western Europe, but he proved unequal to the task. Charles did little to help against Guy, however. Papal letters as late as November were still petitioning Charles for action.

As emperor, Charles began the construction of a palace at Sélestat in Alsace. He modelled it after the Palace at Aachen which Charlemagne, whom he consciously sought to emulate, as indicated by the Gesta Karoli Magni of Notker the Stammerer, had built. As Aachen was in the kingdom of his brother, it was necessary for Charles to build a new palace for his court in his own power base of western Alemannia.[6] Sélestat was also more central to the Empire than Aachen.

In February 882, Charles convoked a diet in Ravenna. The duke, emperor, and pope made peace and Guy and his uncle, Guy of Camerino, vowed to restore stolen papal lands. In a March letter to Charles, John claimed that the vows went unfulfilled. In 883, Guy, now Duke of Spoleto, was accused of treason at an imperial synod held at Nonantula late in May.[7] He returned to Spoleto and made an alliance with the Saracens. Charles sent Berengar, equipped with an army, to deprive Guy of Spoleto. Berengar was initially successful until an epidemic of disease, which ravaged all Italy, affecting the emperor and his entourage as well as Berengar's army, forced him to retire.[7]

In the early 880s, the remnants of the Great Heathen Army, defeated by Alfred the Great at the Battle of Ethandun in 878, began to settle in the Low Countries. Louis, Charles' brother, opposed them with some success, but he died after a short campaign on 20 January 882. Charles succeeded to his kingdom and reunited the whole East Frankish realm again.

When he had returned from Italy, Charles held an assembly at Worms with the purpose of dealing with the Vikings. The army of the whole of East Francia was assembled in the summer under Arnulf, Duke of Carinthia, and Henry, Count of Saxony. The chief Viking camp was besieged at Asselt. Not long after Charles opened negotiations with the Viking chiefs, Godfrey and Sigfred. Godfrey accepted Christian baptism and agreed to become Charles's vassal. He was married to Gisela, daughter of Lothair II. Sigfred was bribed off. Despite the insinuations of some modern chroniclers, no contemporary account criticises Charle's actions during this campaign.[8]

From 882 to 884, the Wilhelminer War dominated the Marcha Orientalis (later Austria). Arnulf of Carinthia, Charles's illegitimate nephew, allied with the rebel Engelschalk II against Charles' appointed margrave in the region, Aribo. Svatopluk I, ruler of Great Moravia, took up Aribo's cause and, in 884 at Kaumberg, took an oath of fidelity to Charles. Though the emperor lost his vassals of the Wilhelminer family and his relationship with his nephew was broken, he gained powerful allies in the Moravian dux and other Slavic duces in the area.

In 885, fearing Godfrey and his brother-in-law, Hugh, Duke of Alsace, Charles arranged for a conference at Spijk near Lobith, where the Viking leader fell into his trap. Godfrey was executed and Hugh was blinded and sent to Prüm.

Charles, childless by his marriage to Richgard, tried to have his illegitimate son by an unknown concubine, Bernard, recognised as his heir in 885, but met the opposition of several bishops. He had the support of Pope Hadrian III, whom he invited to an assembly in Worms in October 885, but who died on the way, just after crossing the river Po.[9] Hadrian was going to depose the obstructing bishops, as Charles doubted he could do this himself, and legitimise Bernard.[9] Based on the unfavouring attitude of the chronicler of the Mainz continuation of the Annales Fuldenses, the chief of Charles's opponents in the matter was probably Liutbert, Archbishop of Mainz. Because Charles had called together the "bishops and counts of Gaul" as well as the pope to meet him at Worms, it seems likely that he planned to make Bernard King of Lotharingia.[10]Notker the Stammerer, who considered Bernard as a possible heir, wrote in his Deeds of Charlemagne:

I will not tell you [Charles the Fat] of this [the Viking sack of the Abbey of Prüm] until I see your little son Bernard with a sword girt to his thigh.[10]

Perhaps Notker was awaiting Bernard's kingship, when Prüm would be avenged.

After the failure of his first attempt, Charles set about to try again. He had the term proles (offspring) inserted into his charters as it had not been in previous years, probably because he desired to legitimise Bernard.[11] In early 886, Charles met the new Pope Stephen V and probably negotiated for the recognition of his son as his heir. An assembly was planned for April and May of the next year at Waiblingen. Pope Stephen cancelled his planned attendance on 30 April 887. Nevertheless, at Waiblingen, Berengar, who by a brief feud with Liutward had lost the favour of the emperor, came in early May 887, made peace with the emperor, and compensated for the actions of the previous year by dispensing great gifts.[12]

Charles probably abandoned his plans for Bernard and instead adopted Louis of Provence as his son at an assembly at Kirchen in May.[13] It is possible, however, that the agreement with Louis was only designed to engender support for Bernard's subkingship in Lotharingia. In June or July Berengar arrived in Kirchen, probably pining to be declared Charles's heir; he may in fact have been so named in Italy, where he was acclaimed (or made himself) king immediately after Charles's deposition.[14]Odo, Count of Paris, may have had a similar purpose in visiting Charles at Kirchen.[14] On the other hand the presence of these magnates at these two great assemblies may merely have been necessary to confirm Charles' illegitimate son as his heir (Waiblingen), a plan which failed when the pope refused to attend, and then to confirm Louis instead (Kirchen).[15]

When Carloman II of West Francia died on 12 December 884, the nobles of that kingdom invited Charles to assume the kingship. Charles gladly accepted, it being the third kingdom to "fall into his lap."[16] According to the Anglo-Saxon Chronicle, Charles succeeded to all of the kingdom of Carloman save Brittany, but this does not seem to have been true.[17] It is likely that Charles was crowned by Geilo, Bishop of Langres, as rex in Gallia on 20 May 885 at Grand in the Vosges in southern Lorraine.[18] Though Geilo even developed a special West Frankish seal for him, Charles's government in the West was always very impersonal and he left most day-to-day business to the higher nobility.

Though West Francia (the future France) was far less menaced by the Vikings than the Low Countries, it was heavily hit nonetheless. In 885, a huge fleet led by Sigfred sailed up the Seine, for the first time in years, and besieged Paris. Sigfred demanded a bribe again, but this time Charles refused. He was in Italy at the time and Odo, Count of Paris, sneaked some men through enemy lines to seek his aid. Charles sent Henry of Saxony to Paris. In 886, as disease began to spread through Paris, Odo himself went to Charles to seek support. Charles brought a large army and encircled the army of Rollo and set up a camp at Montmartre. However, Charles had no intention of fighting. He sent the attackers up the Seine to ravage Burgundy, which was in revolt. When the Vikings withdrew from France next spring, he gave them 700 pounds of promised silver. Charles' prestige in France was greatly diminished.

Charles issued a number of charters for West Frankish recipients during his stay in Paris during and after the siege. He recognised rights and privileges granted by his predecessors to recipients in the Spanish March and Provence, but especially in Neustria, where he had contact with Nantes at a time when the Breton dukeAlan I was known to be powerful in the county of Nantes. It is probable that Charles granted Alan the right to be titled rex;[17] as emperor he would have had that prerogative and Alan's use of the title appears legitimate. A charter datable to between 897 and 900 makes reference to the soul of Karolus on whose behalf Alan had ordered prayers to be said in the monastery of Redon. This was probably Charles the Fat.

With Charles increasingly seen as spineless and incompetent, matters came to a head in late 887. In the summer of that year, having given up on his son's succession, Charles received Odo and Berengar, Margrave of Friuli, a relative of his, at his court. He may have accepted neither, one, or both of these as his heir in their respective kingdoms. His inner circle then began to fall apart. First, he accused his wife Richgard of having an affair with his chief minister and archchancellor, Liutward, bishop of Vercelli. She proved her innocence in an ordeal of fire and left him for the monastic life.[19] He then turned against Liutward, who was hated by all, and removed him from office, appointing Liutbert, Archbishop of Mainz, in his stead.

In that year, his first cousin once removed, Ermengard, daughter of the Emperor Louis II and wife of Boso of Provence, brought her son Louis to him for protection. Charles confirmed Louis in Provence (he may even have adopted him) and allowed them to live at his court. He probably intended to make Louis heir to the whole realm and the imperium. On 11 November, he called an assembly to Frankfurt. While there he received news that an ambitious nephew, Arnulf of Carinthia, had fomented a general rebellion and was marching into Germany with an army of Bavarians and Slavs. The next week saw the collapse of all his support in East Francia. The last to abandon him were his loyal Alemanni, though the men of Lotharingia never seem to have formally accepted his deposition. By 17 November, Charles was out of power, though the exact course of events is unknown. Aside from rebuking his faithlessness, he did little to prevent Arnulf's move—he had recently been ill again—but assured that Bernard was entrusted to his care and possibly Louis too. He asked for a few estates in Swabia on which to live out his days and thus received Naudingen (Donaueschingen). There he died six weeks later, on 13 January 888.

The Empire fell apart, never to be restored. According to Regino of Prüm, each part of the realm elected a "kinglet" from its own "bowels"—the bowels being the regions inside the realm. It is probable that Arnulf desired the whole empire, but the only part he received other than East Francia was Lotharingia. The French elected Odo, though he was opposed at first by Guy III of Spoleto, who also opposed Arnulf in Lotharingia. Guy sought the kingship in Italy after his failures in Francia, though there Berengar had already been crowned. Louis was crowned in Provence as Charles had intended and he sought the support of Arnulf and gained it, probably through supplication to him. Odo would eventually submit to Arnulf's supremacy as well. In Upper Burgundy, one Rudolph, a dux of the region, was elected as king in a distinctly non-Carolingian creation, probably the result of his failure to succeed in the whole of Lotharingia. In Aquitaine, Ranulf II declared himself king and took the guardianship of the young Charles the Simple, the Carolingian heir to the West, refusing to recognise Odo's election.

It is unknown if these elections were a response to Charles's East Frankish deposition or to his death. Only those of Arnulf and Berengar can be certainly placed before his death. Only the magnates of the East ever formally deposed him. He was buried with honour in Reichenau after his death and the Annales Fuldenses heap praises on his piety and godliness. Indeed, contemporary opinion of Charles is consistently kinder than later historiography, though it is a modern suggestion that his lack of apparent successes is the excusable result of near constant illness and infirmity.

Charles was the subject of a hortative piece of Latin prose, the Visio Karoli Grossi, designed to champion the cause of Louis the Blind and warn the Carolingians that their continued rule was not certain if they did not have "divine" (i.e. ecclesiastical) favour.